-- File: full_add.adb (actually full_add2 to store duplicate implementations)
-- Author: Sy Wong
-- Date: 7/98
-- Aim: Implements a one bit adder 


with NOR, 
     INVERT, 
     NAND, 
     X_OR;
package body FULL_ADD is
  procedure update(d: in out device) is
    unit1, unit2: X_OR.device;
    unit3, unit4: NOR.device;
    unit5, unit6: NAND.device;
    unit7, unit8, unit9, unit10: INVERT.device;
  begin
--    d.sum := d.input1 xor d.input2 xor d.carry_in;
--                 unit1      unit2
--    d.cout:= ((d.input1 or d.input2) and d.carry_in) or (d.unit1 and d.nit2);
--               unit3,unit7    unit5,unit8      unit4,unit9    unit6,unit10

    unit1.input1:= d.input1;
    unit1.input2:= d.input2;
    X_OR.update(unit1);
    unit2.input1:= unit1.data_out;
    unit2.input2:= d.carry_in;
    X_OR.update(unit2);
    d.sum:= unit2.data_out;
 
    unit3.input1:= d.input1;
    unit3.input2:= d.input2;
    NOR.update(unit3);
    unit7.data_in:= unit3.data_out;
    INVERT.update(unit7);
    unit5.input1:= unit7.data_out;
    unit5.input2:= d.carry_in;
    NAND.update(unit5);
    unit8.data_in:= unit5.data_out;
    INVERT.update(unit8);
    unit4.input1:= unit8.data_out;
    
    unit6.input1:= d.input1;
    unit6.input2:= d.input2;
    NAND.update(unit6);
    unit10.data_in:= unit6.data_out;
    INVERT.update(unit10);
    unit4.input2:= unit10.data_out;
    NOR.update(unit4);
    unit9.data_in:= unit4.data_out;
    INVERT.update(unit9);
    d.carry_out:= unit9.data_out;    
  end update;
end FULL_ADD;